This invention pertains to an inkjet printing method for achieving high gloss and DOI with pigmented inkjet inks.
Inkjet printing is a non-impact printing process in which droplets of ink are deposited on print media, such as paper, to form the desired image. The droplets are ejected from a printhead in response to electrical signals generated by a microprocessor. Inks used in such recording are subject to rigorous demands including, for example, good dispersion stability, ejection stability, and good fixation to media.
Inkjet printers offer low cost, high quality printing and have become a popular alternative to other types of printers such as laser printers. The resolution of current generation Inkjet printers is so good that they are also replacing many of the traditional photographic printing techniques.
Both dyes and pigments have been used as colorants for inkjet inks. While dyes are typically easy to formulate and offer vivid color, they tend to fade quickly and lack water fastness. Pigments offer good light-fastness and good color, under proper conditions, but the formulation and application of pigment inks is challenging.
The fade-resistant properties of pigments is particularly advantageous for photographic or “photo quality” prints. These types of prints are often expected to last many years and are exposed to long periods of direct light.
The present generation of photo quality printers typically employs scanning printheads. With this type of printing, the printhead can, and usually does, pass over the same area many times, interlacing the drops of ink. Also, in scanning, printheads can achieve higher resolution than would otherwise be possible. Thus a printhead may have nozzles spaced at 180 dpi (180 “native” dpi) but by microstepping the media and making four passes, an apparent resolution of 720 can be achieved.
High Gloss and Distinctness of Image (DOI) are desirable attributes of photo quality images. These attributes are largely influenced by the choice of media, but also playing a role is the choice of ink. Generally, lower gloss and DOI is attained with pigments inks than with dye inks.
The problem of low gloss with pigment inks is noted, for instance, in U.S. Pat. No. 6,857,733, the disclosure of which is incorporated by reference herein for all purposes as if fully set forth. That art is directed to achieving uniform gloss, not necessarily high gloss.
There is still a need for a method of creating high gloss, high DOI inkjet prints with pigment inks.